Multimodal laparoscopic coincidence gamma imaging system for near-infrared fluorescence guided surgery: a preclinical study.

Abstract

Minimally invasive surgery has advantages in terms of quality of life and patient outcomes. Recently, near-infrared (NIR) fluorescence guided surgery has widely used for preclinical and clinical trials. However, NIR fluorescence has a maximum penetration capability of 10mm. Radiographic imaging can be a solution to overcome the depth issue of NIR fluorescence. For this reason, the performance of the multimodal imaging system, which integrates annihilation gamma (511keV) rays, NIR fluorescence, and color images, was evaluated. The multimodal imaging system consisted of a laparoscopic module, containing an internal detector for annihilation gamma events and cameras for optical imaging, and a flat module for coincidence detection with the internal detector. The acquired images were integrated by an algorithm with post image processing and registration. To evaluate the performance of the proposed multimodal imaging system, the images of a resolution target, a square bar target filled with a fluorescence dye, and a sodium-22 point source were analyzed. A preclinical test for axillary sentinel lymph node (SLN) biopsy with a rat model was conducted. The spatial resolution of color images was equivalent to 4 lp/mm. The modulation transfer function of NIR fluorescence at 1 lp/mm was 0.83. The 511keV gamma sensitivity and spatial resolution of the point source were 0.54cps/kBq and 2.1mm, respectively. The image of 511keV gamma rays showed almost the same intensity regardless of the thickness of the tissue phantom. In the preclinical test, an integrated image of the SLN sample of the rat model was obtained with the proposed multimodal imaging system. With the proposed laparoscopic system, a merged image of the sample was obtained with the rat model. The annihilation gamma rays showed penetration capability with the tissue-mimicking phantom superior to that of NIR fluorescence.